Turbine blade

ABSTRACT

An airfoil comprises one or more internal cooling circuits. The cooling circuits can be fed with a flow of cooling fluid from one or more cooling air inlet passages in fluid communication with the cooling circuits. The cooling circuits can further comprise a leading edge cooling circuit defined by a supply passage, a pin bank passage divided into one or more sub-circuits by pin banks disposed within the pin bank passage, and at least first and second cooling passages. The cooling circuits can provide the cooling fluid flow within the airfoil to cool the airfoil, as well as provide a cooling fluid to a plurality of film holes to create a cooling film on the external surface of the airfoil.

BACKGROUND OF THE INVENTION

Turbine engines, and particularly gas or combustion turbine engines, are rotary engines that extract energy from a flow of combusted gases passing through the engine onto a multitude of rotating turbine blades. Gas turbine engines have been used for land and nautical locomotion and power generation, but are most commonly used for aeronautical applications such as for aircraft, including helicopters. In aircraft, gas turbine engines are used for propulsion of the aircraft. In terrestrial applications, turbine engines are often used for power generation.

Gas turbine engines for aircraft are designed to operate at high temperatures to maximize engine efficiency, so cooling of certain engine components, such as the high pressure turbine and the low pressure turbine, can be beneficial. Typically, cooling is accomplished by ducting cooler air from the high and/or low pressure compressors to the engine components that require cooling. Temperatures in the high pressure turbine are around 1000° C. to 1360° C. and the cooling air from the compressor is around 500° C. to 700° C. While the compressor air is a high temperature, it is cooler relative to the turbine air, and can be used to cool the turbine.

Contemporary turbine blades generally include one or more interior cooling circuits for routing the cooling air through the blade to cool different portions of the blade, and can include dedicated cooling circuits for cooling different portions of the blade, such as the leading edge, trailing edge and tip of the blade.

BRIEF DESCRIPTION OF THE INVENTION

An airfoil for a gas turbine engine. The airfoil having an outer surface defining a pressure side and a suction side extending axially between a leading edge and a trailing edge and extending radially between a root and a tip. The airfoil comprises a cooling circuit located within the airfoil, comprising: a supply passage extending from the root toward the tip and fluidly coupled to the dovetail inlet passage at the root; a pin bank passage in fluid communication with the supply passage and extending between the root and the tip, with a plurality of pins located within the pin bank passage and functionally dividing the pin bank passage into at least first and second sub-circuits; and at least first and second cooling passages fluidly coupled to a corresponding one of the first and second sub-circuits and arranged on opposite sides of the pin bank passage. The cooling air from the inlet passage travels through the supply passage in a first radial direction, returns through the sub-circuits in a second radial direction, opposite the first radial direction, and then flows through the first and second cooling passages in the first radial direction.

A blade for a gas turbine engine having a turbine rotor disk. The blade comprises a dovetail having at least one cooling air inlet passage and configured to mount to the turbine rotor disk, and an airfoil extending radially from the dovetail and having an outer surface defining a pressure side and a suction side extending axially between a leading edge and a trailing edge and extending radially between a root and a tip, with the root being adjacent the dovetail. The blade comprises a leading edge cooling circuit located within the airfoil adjacent the leading edge and comprising a supply passage extending from the root toward the tip and fluidly coupled to the dovetail inlet passage at the root, a pin bank passage in fluid communication with the supply passage and extending between the root and the tip with a plurality of pins located within the pin bank passage, and at least first and second cooling passages fluidly coupled to the pin bank passages on opposite sides of the pin bank passage. The supply passage, pin bank passage, and first and second cooling passages are located between the supply passage and the outer surface to collectively define a near surface cooling zone adjacent the outer surface. Cooling air form the inlet passage travels through the supply passage in a first radial direction from root to tip, returns through the pin bank in a second radial direction, opposite of the first radial direction, and then flows through the first and second cooling passages in the first radial direction.

A blade for a gas turbine engine having an airfoil defining a pressure side and a suction side, extending chord-wise between a leading edge and a trailing edge, and extending span-wise between a root and a tip. A near wall cooling circuit comprises a pin bank passage adjacent one of the pressure side and suction side, extending between the root and the tip, with a plurality of pins located within the pin bank passage and functionally dividing the pin bank passage into at least first and second sub-circuits, and at least first and second cooling passages fluidly coupled to a corresponding one of the first and second sub-circuits and arranged on opposite side of the pin bank passage with the pin bank passage and the first and second cooling passages being immediately adjacent one of the pressure side and suction side.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic cross-sectional diagram of a gas turbine engine for an aircraft.

FIG. 2 is a perspective view of a turbine blade of the engine of FIG. 1 including an airfoil attached to a root.

FIG. 3 is a cross-sectional view of the airfoil of FIG. 2.

FIG. 4 is a cross-sectional diagram of the airfoil of FIG. 3 illustrating passages within the interior defining cooling circuits.

FIG. 5 is a close up view of a leading edge cooling circuit of FIG. 4.

FIG. 6 is a flow diagram of the blade of FIG. 4.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The described embodiments of the present invention are directed to a turbine blade, and in particular to cooling a turbine blade. For purposes of illustration, the present invention will be described with respect to a turbine blade for an aircraft gas turbine engine. It will be understood, however, that the invention is not so limited and may have general applicability in non-aircraft applications, such as other mobile applications and non-mobile industrial, commercial, and residential applications. It can also have application to airfoils, other than a blade, in a turbine engine, such as stationary vanes.

FIG. 1 is a schematic cross-sectional diagram of a gas turbine engine 10 for an aircraft. The engine 10 has a generally longitudinally extending axis or centerline 12 extending forward 14 to aft 16. The engine 10 includes, in downstream serial flow relationship, a fan section 18 including a fan 20, a compressor section 22 including a booster or low pressure (LP) compressor 24 and a high pressure (HP) compressor 26, a combustion section 28 including a combustor 30, a turbine section 32 including a HP turbine 34, and a LP turbine 36, and an exhaust section 38.

The fan section 18 includes a fan casing 40 surrounding the fan 20. The fan 20 includes a plurality of fan blades 42 disposed radially about the centerline 12. The HP compressor 26, the combustor 30, and the HP turbine 34 form a core 44 of the engine 10, which generates combustion gases. The core 44 is surrounded by core casing 46, which can be coupled with the fan casing 40.

A HP shaft or spool 48 disposed coaxially about the centerline 12 of the engine 10 drivingly connects the HP turbine 34 to the HP compressor 26. A LP shaft or spool 50, which is disposed coaxially about the centerline 12 of the engine 10 within the larger diameter annular HP spool 48, drivingly connects the LP turbine 36 to the LP compressor 24 and fan 20.

The LP compressor 24 and the HP compressor 26 respectively include a plurality of compressor stages 52, 54, in which a set of airfoils in the form of compressor blades 56, 58 rotate relative to a corresponding set of static airfoils in the form of compressor vanes 60, 62 (also called a nozzle) to compress or pressurize the stream of fluid passing through the stage. In a single compressor stage 52, 54, multiple compressor blades 56, 58 may be provided in a ring and may extend radially outwardly relative to the centerline 12, from a blade platform to a blade tip, while the corresponding static compressor vanes 60, 62 are positioned downstream of and adjacent to the rotating blades 56, 58. It is noted that the number of blades, vanes, and compressor stages shown in FIG. 1 were selected for illustrative purposes only, and that other numbers are possible.

The HP turbine 34 and the LP turbine 36 respectively include a plurality of turbine stages 64, 66, in which a set of airfoils in the form of turbine blades 68, 70 are rotated relative to a corresponding set of static airfoils in the form of turbine vanes 72, 74 (also called a nozzle) to extract energy from the stream of fluid passing through the stage. In a single turbine stage 64, 66, multiple turbine blades 68, 70 may be provided in a ring and may extend radially outwardly relative to the centerline 12, from a blade platform to a blade tip, while the corresponding static turbine vanes 72, 74 are positioned upstream of and adjacent to the rotating blades 68, 70. It is noted that the number of blades, vanes, and turbine stages shown in FIG. 1 were selected for illustrative purposes only, and that other numbers are possible.

In operation, the rotating fan 20 supplies ambient air to the LP compressor 24, which then supplies pressurized ambient air to the HP compressor 26, which further pressurizes the ambient air. The pressurized air from the HP compressor 26 is mixed with fuel in the combustor 30 and ignited, thereby generating combustion gases. Some work is extracted from these gases by the HP turbine 34, which drives the HP compressor 26. The combustion gases are discharged into the LP turbine 36, which extracts additional work to drive the LP compressor 24, and the exhaust gas is ultimately discharged from the engine 10 via the exhaust section 38. The driving of the LP turbine 36 drives the LP spool 50 to rotate the fan 20 and the LP compressor 24.

Some of the ambient air supplied by the fan 20 may bypass the engine core 44 and be used for cooling of portions, especially hot portions, of the engine 10, and/or used to cool or power other aspects of the aircraft. In the context of a turbine engine, the hot portions of the engine are normally downstream of the combustor 30, especially the turbine section 32, with the HP turbine 34 being the hottest portion as it is directly downstream of the combustion section 28. Other sources of cooling fluid may be, but is not limited to, fluid discharged from the LP compressor 24 or the HP compressor 26.

FIG. 2 is a perspective view of an engine component in the form of one of the turbine blades 68 of the engine 10 from FIG. 1. The turbine blade 68 includes a dovetail 76 and an airfoil 78. The airfoil 78 extends from a tip 80 to a root 82. The dovetail 76 further includes a platform 84 integral with the airfoil 78 at the root 82, which helps to radially contain the turbine airflow. The dovetail 76 can be configured to mount to a turbine rotor disk on the engine 10. The dovetail 76 comprises at least one inlet passage, exemplarily shown as a first inlet passage 88, a second inlet passage 90, and a third inlet passage 92, each extending through the dovetail 76 to provide internal fluid communication with the airfoil 78 at a passage outlet 94. It should be appreciated that the dovetail 76 is shown in cross-section, such that the inlet passages 88, 90, 92 are housed within the body of the dovetail 76.

Turning to FIG. 3, the airfoil 78, shown in cross-section, has an interior 96, defined by a concave-shaped pressure sidewall 98, defining a pressure side, and a convex-shaped suction sidewall 100, defining a suction side, which are joined together to define the airfoil shape with a leading edge 102 and a trailing edge 104. The airfoil 78 rotates in a direction such that the pressure sidewall 98 follows the suction sidewall 100. Thus, as shown in FIG. 3, the airfoil 78 would rotate upward toward the top of the page.

The airfoil 78 comprises a plurality of internal passages which can be arranged to form cooling circuits operating as near surface cooling passages, dedicated to cool a particular portion of the blade 68 along an outer surface of the blade. The passages and the corresponding cooling circuits are illustrated in FIG. 4, which is a cross-sectional view of the airfoil 78. It should be appreciated that the respective geometries of each individual passage within the airfoil 78 as shown is exemplary, each depicting one or more elements of a cooling circuit and should not limit the cooling circuits to the geometries, dimensions, or positions as shown.

The cooling circuits can be defined by one or more passages extending radially within the airfoil 78. It should be appreciated that the passages can comprise one or more film holes which can provide fluid communication between the particular passage and the external surface of the airfoil 78, providing a film of cooling fluid along the external surface of the airfoil 78.

As illustrated, the airfoil 78 is provided with three cooling circuits, a leading edge cooling circuit 120, a mid-chord cooling circuit 122, and a trailing edge cooling circuit 124, which can further couple to a first near surface cooling passage, a second near surface cooling passage, and a third near surface cooling passage. The cooling circuits 120, 122, 124 can be supplied with a flow of cooling fluid via the inlet passages 88, 90, 92, respectively, passing through the dovetail 76. The trailing edge cooling circuit 124, as illustrated, further comprises a first cooling circuit 124 a and a second cooling circuit 124 b, commonly fed from the third inlet passage 92. The first and second cooling circuits 124 a, 124 b can further comprise a first near wall cooling passage.

Beginning with the trailing edge cooling circuit 124, the first cooling circuit 124 a and the second cooling circuit 124 b can be commonly fed from the third inlet passage 92 where the third inlet passage 92 can split from one inlet into two inlets within the dovetail 76. In an alternative embodiment, a fourth inlet passage (not shown) can be used to feed one of the first cooling circuit 124 a or the second cooling circuit 124 b while the third inlet passage 92 feeds the other. The second cooling circuit 124 b is disposed adjacent to the trailing edge 104 and the first cooling circuit 124 a is disposed chordially forward of the second cooling circuit 124 b in the aft direction.

The first cooling circuit 124 a comprises a supply passage 130, being in fluid communication with the third inlet passage 92, and extending in a root-to-tip direction. The supply passage 130 fluidly couples to a return passage 132 extending in a tip-to-root direction, which fluidly couples to an outlet passage 134 extending in the root-to-tip direction.

The second cooling circuit 124 b comprises a supply passage 140, being in fluid communication with the third inlet passage 92 and extending in the root-to-tip direction. The supply passage 140 fluidly communicates with a trailing edge passage 142, extending from root-to-tip. In one example, the trailing edge passage 142 can be coupled to the supply passage 140 through one or more inlets 144 extending radially along the airfoil 78, disposed between the supply and trailing edge passages 140, 142. The trailing edge passage 142 can be disposed with one or more rows of pins or pin banks 146 disposed within the trailing edge passage 142. The trailing edge passage 142 can further comprise one or more slots in fluid communication with the trailing edge passage 142 and the exterior of the airfoil 78.

The mid-chord cooling circuit 122 is disposed in the chordial middle of the airfoil 78 relative to the position of the leading edge cooling circuit 120 and the trailing edge cooling circuit 124. The mid-chord cooling circuit 122 can fluidly couple to the second inlet passage 90, receiving a flow of cooling fluid therefrom. The mid-chord cooling circuit 122 comprises a supply passage 160, fluidly coupled to the second inlet passage 90, and extends in the root-to-tip direction. The supply passage 160 can be located adjacent to the suction sidewall 100, or can be adjacent the pressure sidewall 98, or neither adjacent to the pressure 98 nor suction sidewalls 100.

The mid supply passage 160 fluidly couples to a mid plenum passage 162 extending in the tip-to-root direction. The mid plenum passage 162 further couples to a mid return passage 164, being disposed between the combination of the mid supply passage 160 and the mid plenum passage 162, and the leading edge cooling circuit 120. In addition to the mid return passage 164, the mid plenum passage 162 further fluidly couples to a second near surface cooling passage 166 located on the pressure side between the pressure sidewall 98 and the mid plenum passage 162.

The near surface cooling passage 166 comprises a channel 168 having a plurality of pins or a pin bank 170 disposed within the channel 168. The near surface cooling passage 166 is in further fluid communication with a mesh plenum 172 located on an opposite end of the channel 168 relative to where the mid plenum passage 162 fluidly couples to the channel 168.

The leading edge cooling circuit 120 can comprise a supply passage 180, third near surface cooling passage 182, or near surface cooling zone, and leading edge cooling passage 194. The supply passage 180 extends in the root-to-tip direction, being fluidly coupled to the first inlet passage 88 at the outlet 94 to supply the cooling air to the near surface cooling passage 182 and leading edge passage 194. The near surface cooling passage 182 can further define a near surface cooling zone comprising an area of for a flow of a cooling fluid adjacent to the external surface of the airfoil 78, such as the pressure or suction sidewalls 98, 100.

The near surface cooling passage 182 is exemplarily illustrated between the supply passage 180 and the suction sidewall 100, while being adjacent to the suction sidewall 100. In this configuration, the near surface cooling passage 182 cools the wall portion of the airfoil 78 along the suction sidewall 100. Alternatively, the near surface cooling passage 182 can be positioned adjacent to the pressure sidewall 98, between the pressure sidewall 98 and the supply passage 180. Similarly, the supply passage 180, while illustrated as being adjacent to the pressure sidewall 98, can alternatively be positioned adjacent to the suction sidewall 100.

The near surface cooling passage 182 comprises a pin bank passage 186, extending in the tip-to-root direction, and can have a plurality of pins or pin banks 188 disposed within the pin bank passage 186. The near surface cooling passage 182 further comprises at least one return passage 190, illustrated in FIG. 4 as two return passages 190 located on opposite ends of the pin bank passage 186. The return passages 190 fluidly couple to the pin bank passage 186 near the root 82, and extending in the root-to-tip direction. It should be appreciated that the return passages 190 can be turbulated, such as with a plurality of turbulators disposed therein.

The leading edge cooling circuit 120 has a leading edge passage 194, being located adjacent to the leading edge 102 and extending in the root-to-tip direction. The leading edge passage 194 is in fluid communication with the supply passage 180 through an impingement opening 196 defined in a wall 198 between the supply passage 180 and the leading edge passage 194. The leading edge passage 194 can further be adjacent to one return passage 190 of the near surface cooling passage 182.

It should be appreciated that the geometry as illustrated in FIG. 3 is exemplary of one implementation of the cooling circuits disclosed herein and should not be understood as limiting. The cooling circuits comprising a plurality of passages, walls, channels, pin banks, etc. should be understood as one exemplary implementation of the cooling circuits within an airfoil 78, and the positions, dimensions, and geometries disclosed herein are incorporated in order to facilitate understanding of the inventive concept of the cooling circuits. For example, the near wall cooling circuit 182, while shown on the suction sidewall 100 of the airfoil 78, can alternatively be located on the pressure sidewall 98. Similarly, any of the illustrated near wall cooling circuits can be located on the opposite side as illustrated. The number of near wall cooling circuits can be increased and located on both sides. Furthermore, the abstract shapes defined by the passages within the cross-sectional profile of the airfoil 78 are exemplary and can be any shape, geometrical, unique, or otherwise.

Turning to FIG. 5, a close-up view of the leading edge cooling circuit 120 of FIG. 4 best illustrates the cooling passages defining the leading edge cooling circuit 120. The supply passage 180 is in fluid communication with the pin bank passage 186. The plurality of pins 188 disposed within the pin bank passage 186 can be organized into pin banks, such that the pin banks defined sub-circuits. A first sub-circuit 200, second sub-circuit 202, third sub-circuit 204, and fourth sub-circuit 206 can further be defined by the pin banks It should be appreciated that the sub-circuits as illustrated are exemplary and that the pins disposed within the pin bank passage 186 can separate the pin bank passage 186 into two or more sub-circuits. Furthermore, the sub-circuits 200, 202, 204, 206 are not fluidly separated from one another, but can permit the flow of a cooling fluid between the sub-circuits 200, 202, 204, 206 along their radial length.

The return passages 190 can further be defined as first and second cooling passages illustrated as a first return passage 190 a and a second return passage 190 b, respectively. The sub-circuits can further be in fluid communication with the first and second return passages 190 a, 190 b. In the exemplary layout illustrated in FIG. 5, the first and second sub-circuits 200, 202 can be in fluid communication with the first return passage 190 a, and the third and fourth sub-circuits 204, 206 can be in fluid communication with the second return passage 190 b. It should be appreciated that the flow path as described is exemplary and the flow of cooling fluid can pass among sub-circuits 200, 202, 204, 206 as well as to either of the first and second return passages 190 a, 190 b.

The combination of the pin bank passage 186 and the first and second cooling passages can be disposed between the supply passage 180 and the outer surface of the airfoil 78, defining a near-surface cooling zone. As such, near surface cooling zone can be adjacent to at least one of the pressure sidewall 98 or the suction sidewall 100. Alternatively, the near surface cooling zone can be located adjacent to the leading edge 102.

FIG. 6 is a flow diagram for the cooling circuits 120, 122, 124 of the airfoil 78 of FIG. 4. The airfoil 78 is schematically shown in broken line to illustrate the general configuration of the cooling circuit 120, 122, 124 within the airfoil 78. The airfoil 78 defines an airfoil cavity extending from the leading edge 102 to the trailing edge 104 in a chord-wise direction and in the root-to-tip span-wise direction, and which can be divided into distinct channels or passages by internal walls to form the cooling circuits 120, 122, 124, which direct a flow of cooling fluid through the airfoil 78. A tip cooling passage 208, disposed above the tip 80 of the airfoil 78, can extend in a substantially chord-wise direction from near the leading edge 102 toward the trailing edge 104. The tip cooling passage 208 provides a common passage for the cooling circuits 120, 122, 124 to exhaust a cooling fluid, such that cooling fluid fed into the cooling circuits 120, 122, 124 can be eventually exhausted from the airfoil 78 if not being exhausted through one or more film holes 136.

The trailing edge cooling circuit 124 can be fed with a flow of cooling fluid from the third inlet passage 92. The third inlet passage 92, can further supply the first cooling circuit 124 a and the second cooling circuit 124 b individually, which can be done by separating the cooling fluid flow from the third cooling inlet 92 into a leading side inlet 92 a and a trailing side inlet 92 b.

The first cooling circuit 124 a, illustrated as being fed from the leading side inlet 92 a, receives a cooling fluid flow within the supply passage 130 in the root-to-tip direction. At an upper turn 218, the cooling fluid can be provided to the return passage 132 from the supply passage 130, moving in the tip-to-root direction. The cooling fluid can then be provided to the outlet passage 134 from the return passage 132, at a lower turn 220 moving from root-to-tip. Within the outlet passage 134, the cooling fluid can be exhausted through the film holes 136 to provide a cooling film along the exterior surface of the airfoil 78. Thus, the fluid path defined by the first cooling circuit 124 a can be substantially serpentine, snaking between the tip 80 and the root 82.

The second cooling circuit 124 b, illustrated as being fed from the trailing side inlet 92 b, can be provided with a flow of cooling fluid in the supply passage 140 in the root-to-tip direction. Along the supply passage 140, cooling fluid can flow into a trailing edge passage 142, which can comprise one or more pins 146, through one or more inlets 144 from the supply passage 140. Cooling fluid, which does not flow into the trailing edge passage 142, can be exhausted from the tip end 222 of the supply passage out the trailing edge 104 of the airfoil 78.

Cooling air within the trailing edge passage 142 can be exhausted from the airfoil 78 through the film holes 136, or can alternatively be exhausted through the trailing edge 104 through the slots 148.

The mid-chord cooling circuit 122, disposed chordially between the leading edge cooling circuit 120 and the trailing edge cooling circuit 124, can be fed with a flow of cooling fluid from the second inlet passage 90. The mid-chord cooling circuit 122 receives the cooling fluid within the supply passage 160 from the second inlet passage 90, moving from root-to-tip. The mid-chord cooling circuit 122 further comprises an upper turn 214 where the supply passage 160 fluidly communicates with the mid plenum passage 162. The mid plenum passage 162 is further in fluid communication with the near surface cooling passage 166 through the channel 168 from the mid plenum passage 162. The cooling airflow can move through the near surface cooling passage 166, which can include one or more pins or pin banks 170, to the mesh plenum 172, where the cooling fluid can be exhausted through the film holes 136 to create a cooling film along the outer surface of the airfoil 78.

The mid-chord cooling circuit 122 can further comprise a lower turn 216, providing cooling fluid to the mid return passage 164 from the mid plenum passage 162. From the mid return passage 164, the film holes 136 can exhaust the cooling fluid from the mid-chord cooling circuit 122 to provide a cooling film along the exterior surface of the airfoil 78. As the mid return passage 164 can extend between the suction and pressure sidewalls 98, 100, film holes 136 can provide a cooling fluid flow to the exterior surfaces of the airfoil 78.

The leading edge cooling circuit 120 can be fed with the cooling fluid from the first inlet passage 88 within the dovetail 76. The leading edge cooling circuit 120 receives the cooling fluid within the supply passage 180 moving from root-to-tip, comprising a first radial direction. The supply passage 180 fluidly communicates with the leading edge passage 194 through the impingement openings 196 where the film holes 136 can exhaust the cooling fluid along the leading edge 102 of the airfoil 78 to create a cooling film.

The leading edge cooling circuit 120 can further include at least one upper turn 210 near the tip 80, providing cooling fluid to the pin bank passage 186 from the supply passage 180. At the upper turn 210, the cooling fluid can flow from the supply passage 180 into pin bank passage 186. The cooling fluid travels within the pin bank passage 186, comprising multiple pins 188, in the tip-to-root direction, comprising a second radial direction being opposite of the first radial direction. The pins 188 within the pin bank passage 186 further separates the pin bank passage 186 into the sub-circuits 200, 202, 204, 206. The flow of cooling fluid moves within the sub-circuits 200, 202, 204, 206 in the tip-to-root direction. Near the root 82, the leading edge cooling circuit 120 can further comprise at least one lower turn 212, exemplarily illustrated as two lower turns 212, providing cooling fluid from the pin bank passage 186 to the first and second return passages 190 a, 190 b. The cooling fluid flows within the return passages 190 a, 190 b in the root-to-tip direction, being the first radial direction, and can exhaust the cooling fluid through the film holes 136 to form a cooling film along the airfoil 78 exterior surface or to the tip cooling passage 208.

It should be appreciated that cooling circuits 120, 122, 124, as illustrated in FIG. 4 are exemplary of one implementation of the cooling circuits within an airfoil 78 and should not be construed as limited by the particular geometry, passages, pin banks, film holes, etc. It should be further understood that while the cooling circuits 120, 122, 124, 124 a, 124 b are illustrated as generally moving from the leading edge 102 toward the trailing edge 104 or the trailing edge 104 toward the leading edge 102, the illustration is only an exemplary depiction of the cooling circuits themselves. The particular passages, channels, inlets, or mesh can flow in any direction relative to the airfoil 78, such as in the leading or trailing edge 102, 104 direction, tip 80 or root 82 direction, or toward the pressure or suction sidewalls 98, 100 of the airfoil 78, or any combination thereof.

The various embodiments of systems, methods, and other devices disclosed herein provide improved cooling effectiveness for the near surface cooling zone or cooling circuit of a turbine blade. One advantage that may be realized in the practice of some embodiments of the described systems is that the cooling circuits of the blade can be utilized to at least one of pressure or suction sidewalls of the blade, and more preferably on both sidewalls, while providing air to the film holes in order to create a cooling film on the external surface of the airfoil. The implemented cooling circuits provide optimal cooling and airflow management within an airfoil, in order to maintain effective engine operation at heightened temperatures, increasing engine efficiency and lifetime.

This written description uses examples to disclose the invention, including the best mode, and to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and can include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. 

What is claimed is:
 1. An airfoil for a gas turbine engine, the airfoil comprising: an outer surface defining a pressure side and a suction side extending axially between a leading edge and a trailing edge and extending radially between a root and a tip; and a cooling circuit located within the airfoil and comprising: a supply passage extending from the root toward the tip and fluidly coupled to the cooling air inlet passage at the root, a pin bank passage in fluid communication with the supply passage and extending between the root and the tip, with a plurality of pins located within the pin bank passage and functionally dividing the pin bank passage into at least first and second sub-circuits, and at least first and second cooling passages fluidly coupled to a corresponding one of the first and second sub-circuits and arranged on opposite sides of the pin bank passage; wherein cooling air from the cooling air inlet passage travels through the supply passage in a first radial direction, returns through the sub-circuits in a second radial direction, opposite the first radial direction, and then flows through the first and second cooling passages in the first radial direction.
 2. The airfoil according to claim 1 wherein the pin bank passage and the first and second cooling passages are located between the supply passage and the outer surface.
 3. The airfoil according to claim 2 wherein the pin bank passage and the first and second cooling passages are located adjacent the outer surface to define a near-surface cooling zone.
 4. The airfoil according to claim 3 wherein the near surface cooling zone is located adjacent at least one of the pressure side and suction side.
 5. The airfoil according to claim 4 wherein the near surface cooling zone is located adjacent the suction side.
 6. The airfoil according to claim 4 wherein the near surface cooling zone is located adjacent the leading edge.
 7. The airfoil according to claim 6 wherein the cooling circuit further comprises a leading edge cooling passage fluidly coupled to the supply passage and extending along the leading edge.
 8. The airfoil according to claim 7 wherein the leading edge cooling passage is adjacent one of the first and second cooling passages.
 9. The airfoil according to claim 8 further comprising a plurality of film holes extending from the first and second passages to the outer surface.
 10. The airfoil according to claim 9 wherein the pin bank passage has no film holes extending to the outer surface.
 11. A blade for a gas turbine engine having a turbine rotor disk, the blade comprising: a dovetail having at least one cooling air inlet passage and configured to mount to the turbine rotor disk; an airfoil extending radially from the dovetail and having an outer surface defining a pressure side and a suction side extending axially between a leading edge and a trailing edge and extending radially between a root and a tip, with the root being adjacent the dovetail; and a leading edge cooling circuit located within the airfoil adjacent the leading edge and comprising: a supply passage extending from the root toward the tip and fluidly coupled to the cooling air inlet passage at the root, a pin bank passage in fluid communication with the supply passage and extending between the root and the tip, with a plurality of pins located within the pin bank passage, and at least first and second cooling passages fluidly coupled to the pin bank passage and arranged on opposite sides of the pin bank passage; wherein the pin bank passage, and first and second cooling passages define a near surface cooling zone and are located between the supply passage and the outer surface adjacent the outer surface, and cooling air from the cooling air inlet passage travels through the supply passage in a first radial direction from root-to-tip, returns through the pin bank in a second radial direction, opposite the first radial direction, and then flows through the first and second cooling passages in the first radial direction.
 12. The blade according to claim 11 and further comprising a leading edge cooling passage fluidly coupled to the supply passage and extending along the leading edge and located between the supply passage and the leading edge.
 13. The blade according to claim 12 wherein the near surface cooling zone is located adjacent at least one of the pressure side and suction side.
 14. The blade according to claim 13 wherein the near surface cooling zone is located adjacent the suction side.
 15. The blade according to claim 14 wherein the supply passage is adjacent the pressure side.
 16. The blade according to claim 11 further comprising a plurality of film holes extending from the first and second passages to the outer surface.
 17. The blade according to claim 16 wherein the pin bank passage has no film holes extending to the outer surface.
 18. The blade according to claim 11 wherein the dovetail comprises a second cooling air inlet passage and further comprising a trailing edge cooling circuit having a second supply passage fluidly coupled to the second cooling air inlet passage, and at least one second near surface cooling passage fluidly coupled to the second supply passage and located adjacent the outer surface.
 19. The blade according to claim 18 wherein the dovetail comprises a third cooling air inlet passage and further comprising a mid-chord cooling circuit, located chord-wise between the leading edge and trailing edge cooling circuits, and having a third supply passage fluidly coupled to the third cooling air inlet passage, and at least one third near surface cooling passage fluidly coupled to the third supply passage and located adjacent the outer surface.
 20. The blade according to claim 19 wherein the third near surface cooling passage is located adjacent an opposite one of the pressure side and suction side than the near surface cooling zone of the leading edge circuit. 